1. Field of the Invention
The present invention relates to a magnetic material for high frequencies and, more particularly, to a magnetic composition of a calcium vanadium garnet system suitable for use in a range of high frequencies such as microwaves and millimeter-waves.
2. Description of the Prior Art
As a magnetic material for high frequencies, there have been used those such as manganese-magnesium ferrites, nickel-zinc ferrites, lithium ferrites and yttrium-irongarnets (YIG), calcium-vanadium-garnets, etc since they have a saturation magnetization (4.pi.Ms) ranging from 500 to 4000 gauss. Among them, calcium-vanadium-garnets are known to be a magnetic material with a low magnetic loss which is given by a ferromagnetic resonance absorption half-line width (.DELTA.H). Thus, the calcium-vanadium-garnets make it possible to produce low-loss circuit elements such as isolators and circulators since they meet requirements for magnetic materials to be used for such purposes such that they must have not only a suitable value of 4.pi.Ms but a small .DELTA.H.
Japanese patent publication No. 56-31289 (JP-B-56-31289) discloses a magnetic material of a system (Ca.sub.3-y Y.sub.y) (Fe.sub.2-x In.sub.x) (Fe.sub.1.5+0.5y-0.5z Si.sub.z V.sub.1.5-0.5x-0.5z)O.sub.12 with low .DELTA.H, produced by replacing a part of Ca in a calcium-vanadium-garnet with Y and replacing a part of Fe with In and Si.
On the other hand, it has been reported by H. J. Van Hook and J. J. Green, "linewidth Reduction through Indium Substitution in Calcium-Vanadium Garnets", in Journal of Applied Physics, Vol. 39, No. 2, p730, 1968, that yttrium and indium substitutions in calcium-vanadium-garnets causes variations of 4.pi.Ms, decrease of the anisotropic field and reduction of .DELTA.H.
However, the above calcium-vanadium-garnets have a serious problem that a slight deviation of the composition causes considerable increase in both .DELTA.H and dielectric dissipation factor (tan .delta.) and thus interferes with practical uses.
Further, when the magnetic material is used for self-biased phase converting elements or latching type phase shifters, it is required to have a large ratio of remanent magnetic flux density (Br) to maximum magnetic flux density (Bm), i.e., a large squareness ratio (Br/Bm), as well as small tan .delta.. However, the above calcium-vanadium-garnet materials cannot be applied to the phase converting elements since the greater Br/Bm the greater is tan .delta. and since the smaller the tan .delta. the smaller is Br/Bm.